Research objectives: (1) To isolate and determine the structures of the in vivo active antitumor principles of the selected plant extracts. (2) To investigate the relationships between the structures of the active principles and their antitumor activity. (3) To further modify the novel antitumor structures as well as the synthesis of the analogs as an approach to make possible useful anticancer agents. Research methods: (1) The plant extracts which have been used in folklore remedies for cancer as well as those with reputed biomedical properties in Taiwan and elsewhere will be screened for in vivo antitumor activity against P-388 and L-1210 leukemias as well as Walker 256 carcinosarcoma. (2) Only those in vivo active extracts will be selected as suitable candidates for further chemical studies which include the isolation and structural determination of the active antitumor principles. Extracts of 15 different plant species in 10 families have been chosen for this purpose. (3) Extraction, fractionation and isolation of the active principles will be guided at every stage by an in vitro cytotoxicity assay in H.Ep.-2 or KB cells. (4) Modern physical methods such as UV, IR, NMR, C-13 NMR, ORD, CD, mass spectroscopy and x-ray crystallographic analysis as well as elemental analysis will be used to elucidate and confirm the complete structures of the active principles isolated. (5) Studies on structure modification in the course of structural elucidation and synthesis of analogs for the active principles with novel structures will be added in order to investigate the structure-activity relationships as well as possible discovery of new useful antitumor agents.